Teramura Yuji, Iwata Hiroo
Department of Nano-Medicine Merger Education Unit, Graduate School of Engineering, Kyoto University, and Institute for Frontier Medical Sciences, Kyoto University, 53 Kawara-cho, Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan.
Bioconjug Chem. 2008 Jul;19(7):1389-95. doi: 10.1021/bc800064t. Epub 2008 Jun 6.
Transplantation of islets of Langerhans (islets) is a promising technique for treating insulin-dependent diabetes mellitus (type I). One unresolved issue is early graft loss due to inflammation triggered by blood coagulating on the surface of islets after transplantation into the portal vein. Here, we describe a versatile method for modifying the surface of islets with an ultrathin membrane carrying the fibrinolytic enzyme urokinase or the anticoagulant heparin. The surface of islets was modified with a poly(ethylene glycol)--phospholipid conjugate bearing a biotin group (biotin-PEG-lipids, PEG MW: 5000). Biotin-PEG-lipids were anchored to the cell membranes of islets, and the PEG-lipid layer on the islets was further covered by streptavidin and biotin-bovine serum albumin conjugate using a layer-by-layer method. The surface was further activated with oxidized dextran. Urokinase was anchored to the islets through Schiff base formation. Heparin was anchored to the islets through polyion complex formation between anionic heparin and a cationic protamine coating on the islets. No practical islet volume increase was observed after surface modification, and the modifications did not impair insulin release in response to glucose stimulation. The anchored urokinase retained high fibrinolytic activity, which could help to improve graft survival by preventing thrombosis on the islet surface.
胰岛移植是治疗胰岛素依赖型糖尿病（I型）的一种很有前景的技术。一个尚未解决的问题是，将胰岛移植到门静脉后，由于胰岛表面血液凝固引发炎症导致早期移植物丢失。在此，我们描述了一种通用方法，可通过携带纤溶酶尿激酶或抗凝剂肝素的超薄膜对胰岛表面进行修饰。胰岛表面用带有生物素基团的聚（乙二醇）-磷脂共轭物（生物素-聚乙二醇-脂质，聚乙二醇分子量：5000）进行修饰。生物素-聚乙二醇-脂质锚定在胰岛细胞膜上，胰岛上的聚乙二醇-脂质层通过层层组装法进一步被链霉亲和素和生物素-牛血清白蛋白共轭物覆盖。表面用氧化葡聚糖进一步活化。尿激酶通过席夫碱形成锚定在胰岛上。肝素通过胰岛上阴离子肝素与阳离子鱼精蛋白涂层之间形成聚离子复合物而锚定在胰岛上。表面修饰后未观察到胰岛实际体积增加，且修饰并未损害胰岛对葡萄糖刺激的胰岛素释放。锚定的尿激酶保留了高纤溶活性，这有助于通过防止胰岛表面血栓形成来提高移植物存活率。
